The chemical basis for interaction between steroid hormones and specific serum proteins is being investigated. Progesterone-binding globulin and alpha-glycoprotein have been isolated as homogeneous proteins. They are being studied by physicochemical and chemical methods for relationship of chemical structure to steroid binding. Bibliographic references: Westphal, U. Binding of Corticosteroids by Plasma Proteins. Handbook of Physiology, Section on Endocrinology (E.B. Astwood and R.O. Greep, Eds.) Section 7: Endocrinology, Vol. VI. Adrenal Gland, pp. 117-125. Am. Physiol. Soc., Washington, D.C. 1975. Westphal, U. Steroid Binding to Proteins: Some Open Questions. In "Normal and Abnormal and Abnormal Growth of the Prostate", (M. Goland, Ed.), pp. 616-631. C.C. Thomas, Springfield, 111. 1975.